


Their Lullaby

by Plagg



Category: Miraculous Ladybug
Genre: Age Regression/De-Aging, F/M, Non-Sexual Age Play, but ao3 doesn't have a proper tag for only age regression, this is about age regression not age play
Language: English
Status: In-Progress
Published: 2020-04-11
Updated: 2020-06-29
Packaged: 2021-03-02 02:22:21
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 5
Words: 3,298
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23597542
Author URL: https://archiveofourown.org/users/Plagg/pseuds/Plagg
Summary: Luka thought back on all the ways Marinette could be quite childish.  She could be the silliest, giggliest thing on the planet sometimes, much like a child, and her tears over the past few weeks could even be apart of it.  He’d have to research more, and perhaps study Marinette a bit more, but if he was right…he felt even worse for her.  If this was what was going on with Marinette, then Luka would be right there for her whenever she needed him.  And if it wasn’t, then perhaps this could help her cope with what was truly wrong?
Relationships: Luka Couffaine/Marinette Dupain-Cheng | Ladybug
Comments: 25
Kudos: 118





	1. Chapter 1

**Author's Note:**

> it's been a while since i've properly written for miraculous ladybug, or written at all for that matter, so please go easy on me lol

There was a certain comfort Luka had begun to find in the lumpy, certainly _un_ comfortable chaise Marinette had in her room. He wasn’t sure why it had started to become comfortable, but he supposed that after several weeks of laying there for hours on end, he’d gotten used to the seat. What was uncomfortable was the cold dampness of his shirt where Marinette had been crying, sobbing on him for the past…however long.

At this point, it was routine. Luka would come over after school, he and Marinette would do homework and work on Kitty Section together for just over an hour before Luka would ask what was going on in Marinette’s world, only for her to either brush it off or start to cry. He hated that he was used to her tears at this point, that he’d come to expect them whenever he came over. But at least, he thought, she had someone to go to.

And the end of that routine was precisely where they were now, with Marinette’s makeup officially ruined along with the neckline of Luka’s shirt. Slowly, ever so slowly, her tears began to soften, and they dissolved into not much more than hiccups and sniffles.

“Are you feeling better, now?” Luka asked. Marinette gave a tiny nod and lifted her head off his chest, closing her eyes when he wiped her cheeks with his thumb. “Did you want to talk about it this time?” He always asked, but Marinette never took him up on the offer.

Marinette let out a shaky sigh and shook her head. She wiped at her eyes as she wished for the umpteenth time since this started that she could tell him about all of her troubles. She wished so badly that she could tell Luka everything, tell him how she doesn’t feel suited to be the Guardian of the Miracle Box, tell him about her fears as Ladybug and her troubles with Adrien, or Chat Noir, or _anything_.

But she couldn’t. Ladybug was a secret, and at this point Marinette was absolutely sure she would break completely if she lost Ladybug, lost _Tikki_.

“I’ll always be here if you want to talk,” Luka reminded her, and Marinette simply nodded. Well. Luka supposed it was time to finish the rest of the routine. “Do you want some water?” he asked, getting to his feet when he received a nod. He disappeared down the stairs to fetch the girl a drink. Only, this time when he returned, routine broke.

Instead of coming back up to find Marinette curled up with her back against the chaise, he found her laying down with her phone in one hand, and the thumb of her other fixed between her lips. She looked completely exhausted, and Luka reckoned that she _had_ been crying a bit harder than normal. He cleared his throat as he took a seat beside the girl, and she wiggled just enough to make room for Luka to sit.

“Here’s your water,” he said, passing the glass to her.

“Thank you…” Marinette removed her thumb from her mouth, replacing it with the glass as she gulped down the water. “Sorry about all that…again…” Marinette said sheepishly.

Luka chuckled and shook his head. “You don’t need to apologize. I’m glad you can get it all out.”

The two exchanged small smiles and moved on the seat to lay back down together. It was cramped, as always, on the chaise, but they somehow found the arrangement comfortable. Luka placed a hand on Marinette’s back, rubbing small circles and tracing random shapes into her spine. Marinette’s eyes fell closed as she gave into her body’s exhaustion, and not a minute later she fell asleep, her thumb back in her mouth.

Luka didn’t know quite what to think of it. Out of all the times Marinette had stayed the night with Juleka, or out of all the naps she’d had on Luka, he had never noticed her sleep with her thumb in her mouth. It was cute, he decided, but…why was she doing it?

Slowly and carefully, so as not to disturb the sleeping girl on his chest, Luka fished his phone from his pocket and pulled up his search engine. He figured that he might be able to figure something out, perhaps another way to help Marinette, if researched what was going on, and any reason that someone might start sucking their thumb just out of the blue. He type out “my girlfriend sucks her thumb” and hit enter. He figured the search would yield more results than “my friend who is a girl that I want to be my girlfriend sucks her thumb” could ever hope to yield. And he was right. Several articles and…odd…results later, Luka found some interesting results. He found the phrase age regression, something about “inner child therapy” he’d gathered, and he discovered it was quite common. Many people who suffered trauma or neglect or even just general stress and anxiety found it to be a very helpful coping strategy, and some couldn’t help that it happened.

Well then.

Luka thought back on all the ways Marinette could be quite childish. She could be the silliest, giggliest thing on the planet sometimes, much like a child, and her tears over the past few weeks could even be apart of it. He’d have to research more, and perhaps study Marinette a bit more, but if he was right…he felt even worse for her. If this was what was going on with Marinette, then Luka would be right there for her whenever she needed him. And if it wasn’t, then perhaps this could help her cope with what was truly wrong?

**Notes for the Chapter:**

> so i decided to write this simply because there isn't much in the way of good agere fic in this fandom, and these kids need a break
> 
> also! i have a blog to go along side this fic, you can world build and ask me questions about the au over at @theirlullaby on tumblr!


	2. Chapter 2

**Summary for the Chapter:**

> Luka decides to experiment a bit with the possibility of Marinette regressing with him

The next week, Luka came over to Marinette’s after school just as he normally would, though this time his backpack held something extra. He had been teased, yes, during class when the surprise peaked it’s little head out from his bag, but it’d be worth the slight embarrassment, he was sure. Luka took his usual seat on the floor with his books spread out, snickering as he watched Marinette try to get organized.

She was certainly not one for color-coded notes, meticulously lined up pens and pencils, and Instagram-worthy layouts. Instead, she was a whirlwind of mess and organized chaos. Marinette pulled out her notes with a triumphant “aha!” and settled down beside the snickering Luka. She puffed her cheeks and narrowed her eyes. “What’s so funny!”

“Oh nothing,” Luka said through his snickers. “You’re just a funny girl, Marinette. And cute.”

Marinette dropped her annoyed look, replacing it with a blush, turning her head away and giggling. “L-let’s just get to work!”

The two worked for a while, settling into their normal rhythm. Once they finished with homework, Marinette yawned and stretched out her arms behind herself. “So glad to be finished! I’m so tiiiiiiiired.”

Luka snickered as he put his books away. “What’s got you so tired today?”

Marinette groaned and shook her head. “It’s nothing…just life stuff.” They sat in silence for a few minutes, and like clockwork, Luka saw tears begin to well in the girl’s eyes. “You pro-obably are getting re-eally tired of this,” Marinette said with a sniffle, wiping at her eyes.

“I just wish I knew how to help you feel better…” Luka said. He scooted a bit closer, tugging the girl against his side. “I don’t mind being your shoulder to cry on…I just wish I knew what to do to stop the tears.”

Marinette’s quivering lip betrayed her at that point, and her tears sprang forward with a choked sob. “I-It’s just so much _stuff!_ I can’t do it _all!_ I-I’m not cut out for-for thi-is!”

Luka shushed her, rubbing her shoulder as Marinette cried into his shoulder. He didn’t understand what was going on her head, but he knew he wanted to be there for her. “…Hey, I think I might know something that might help you feel a little better…”

Red-ringed eyes peered up at him through blue bangs, a curious look behind the pupils. Luka took that as a cue, and he unzipped his backpack, fishing out a teddy bear. The teddy bear was dressed in a cute ballerina costume, and it smelled like cupcakes. Marinette gasped when she saw it, and Luka could have sworn he saw her grip at the air for it, if only for a second.

“Here, she’s all yours,” he said, and Marinette squeaked, taking the bear into her arms.

“Th-thank you, Luka…” she said. Immediately, Marinette buried her nose in the fluff of the bear, leaning against Luka’s side. She felt a bit calmer like this, so close to Luka, and with her new bear in her hands. Soon, they started talking about a new song Kitty Section would be recording, and Marinette slipped her thumb into her mouth as Luka kept talking, and soon, with the scent of cupcakes in her nose and the soothing sound of Luka’s humming in her ears, Marinette drifted off to sleep.

Luka smiled down at the girl, kissing her forehead before moving her to the chaise. She looked so peaceful, so happy. Luka wanted so badly to help her feel this happy more often.

**Notes for the Chapter:**

> sorry this is so short, buuuuut two chapters in one day? yay? i'm just excited for this au lol
> 
> we'll start getting into the actual regression stuff soon, buuuut in the meantime, if you want to learn more about the au, come chat with me on tumblr! @theirlullaby


	3. Chapter 3

**Summary for the Chapter:**

> marinette and luka have a spa night

Marinette was just having a truly awful day. She’d been up most of the night with Chat trying to take down an akuma, which landed her in bed for only 30 minutes before her alarm went off. Tikki insisted on her getting up, telling the girl that she’d be late for class if she slept in, not that Marinette would have minded at this point. Then, once at school, Chloe pranked her with a bit of slime in her seat and left her with a wet spot stained onto the seat of her pants. Then, as if that weren’t enough, Marinette was paired with _Lila_ for an assignment.

Her shoulders sagged as she exited the school, glad at least that she didn’t have any homework for the night. She spotted Luka, ever smiling Luka, standing at the bottom of the steps, and a small smile formed on her lips.

“You look like you’ve been run over,” Luka said, taking Marinette’s hand as she reached the bottom of the steps.

“I feel like it too…” she said, fitting herself against the boy’s side as they began walking toward the bakery. “I think today was the worst day ever, in the history of forever.”

Luka couldn’t help but snicker and shook his head. “Sounds like you need a relaxation night, then.”

“More than anything…”

* * *

Once up in Marinette’s room, the girl changed out of her messed up pants, opting for a pink overall dress, paired with a white shirt and fuzzy socks. Luka couldn’t help but find her utterly _adorable_. “Anything you wanna do for this relaxing night?” he asked, and Marinette seemed to ponder her options.

“Maybeeee facemasks and we can paint our nails?” Even though Luka laughed out loud at the suggestion, she knew he’d go along with it. Perks of having a guy friend with a flair for the feminine. So, they ended up both covered in drippy sheet masks that looked like a Panda and a Tiger respectively, and Marinette ended up with pink, glittery nails while Luka’s were all black, save for his blue ring fingers. Marinette giggled when he blew on his nails, kicking her legs in amusement.

“What’s so funny, Marinette?” he asked lightly, which only made the girl giggle again.

“Just you! You’re facemask is almost falling off your nose, the teddy bear headband doesn’t match the kitty-cat face, and you’re blowing on your nails silly!”

Oddly, Luka noted, she seemed to speak with a higher pitch than normal. “Well, if I look so silly, I’m gonna blame the girl sitting right…across…me!” He tugged her chair forward between words, causing the girl to squeal. “Tell me, does my face smell like oranges yet?”

Marinette squeaked and tipped back on her chair, giggling still. “You smell silly!”

“Whaaaaat? What does silly smell like?”

“Like boogers and mulch!”

“I’m offended, Marinette!”

Marinette stuck her tongue out at the boy, and Luka tsked, pushing his sleeves up as he got to his feet. “Ohhhhhh no, she stuck her tongue out! You know what I do to little girls who are mean, Mari?”

“What?” Marinette said, a challenging tone to her voice.

“This!” Luka dove in, tickling Marinette as she squealed and kicked and wriggled around. This was the happiest he had seen her in a long time, not a single tear shed the entire evening, and she was having fun and being just a _little bit_ silly. And, if her tone and method of mockery were anything to go by, he’d say she regressed even without his help. Perhaps she already regressed without meaning to, and his help just made it more prominent. Either way, he was glad to help. Well, and also glad to- “Rawrrrrrrr!” -tickle the girl until she fell off her chair.

**Notes for the Chapter:**

> yeet he's almost ready to bring it up to her, and then we'll get into some Real Regression Vibes after that!


	4. Chapter 4

**Summary for the Chapter:**

> luka tells marinette about regression

Marinette laid beside Luka on her bed, the two comfortably resting and watching a movie on her tablet. She sighed peacefully, her eyelids heavy with happiness and drooping between breath intakes, as she snuggled closer into the boy. Never before had anything felt so right, so _nice_. She hadn’t felt this peaceful since she was a child.

She barely registered the credit music starting as the movie came to a close, rather focusing on the arm around her waist and Luka’s heartbeat. Though, she noticed as the credits went on, his heartbeat seemed to quicken.

“Luka…?” Marinette called, snapping him back to reality. “You okay?”

“Huh? Yeah, I’m fine, Marinette. It’s nothing to worry about.” Luka sat up and mussed his hair, trying to play it cool. He planned on this night being the night he talked to Marinette about the regression thing, he knew he needed to, but as the window of opportunity closed in around them, he grew more and more nervous. How did he even start this conversation? How would Marinette take it? Would she want him to leave, to never talk to her again?

“You seem upset…” Marinette said, and Luka noted the higher pitch. He knew she spoke a little bit differently when she regressed with him, and he didn’t know how talking to her when she was like this would go.

Luka swallowed hard. He just needed to _do it_. “Well…actually…there’s something I need to talk to you about.” Luka noted how quickly the girl tensed up, and he stuttered out that it wasn’t anything bad. “I just…there’s this thing that I think would help you feel better about the stuff going on in your life, and I didn’t know if you know anything about it…”

“What is it…?” Marinette asked.

“Uh…well it’s this therapy thing called age regression, where you mentally revert to a childlike mindset in order to cope with trauma or stress…” Luka explained more of what it was, watching Marinette’s face for her reaction, looking for any sign of disgust or horror.

“…Sounds nice. Do people like that get cute stuffed animals from their friends?” Marinette asked, tugging the bear from Luka onto her lap.

“Sometimes,” Luka said, grinning at Marinette before taking her hand. “More often than not regressors get presents like that from someone they trust to take care of them.”

“Well I trust you…”

“Yeah?” Luka didn’t mean to sound hopeful, but he so desperately wanted to help Marinette, wanted to be there for her and make this as easy as possible for her. He wanted so badly to take care of her.

“And I like having you take care of me like you have been lately…it’s the best I’ve felt in a long time.” Marinette didn’t quite know what the heck Luka was talking about, what the heck “regressing” was, but she was intrigued.

The two cuddled up together and researched, finding information explaining ways people use their regression, and ways to get into it, how to feel younger, and the more cute stuffies and pacifiers, more sippy cups and tutus, Marinette saw, the more she fell in love with this idea. She also may have convinced Luka that she _very desperately_ wanted the cute pastel pink pacifier she saw. Marinette already sucked her thumb, she knew that, so she figured having something cute that she could _decorate_ would be much, much better.

And maybe Luka also found an adorable onesie for the girl to try, since she seemed interested in all the cute patterns. And maybe a sippy cup. And maybe he needed more money. He could worry about that later, though, because at this moment the only thing that mattered to Luka was that his adorable girl was happy. Which, if her giggles and cute kicks when she saw something cute on Instagram was anything to go by, she was the happiest she’d ever been. And he had a hand in it.

**Notes for the Chapter:**

> sorry that this sucks i just can't seem to write well lately kajsdlgadhfjk


	5. Chapter 5

**Summary for the Chapter:**

> marinette gets her paci in the mail

“Lukaaaaa!” Marinette squealed, running down the stairs of the school and leaping at the boy.

“Woah, woah, what’re you so excited about, Marinette?” Luka asked with a snicker. He wrapped an arm around her waist as they began to walk toward the bakery, Luka snickering as the girl bouncing excitedly.

“Looooook!” Marinette shoved her phone in Luka’s face, showing him the very exciting tracking number displayed on the screen.

“Oh, did it come already?” he asked, and she nodded about 20 times a second if he wasn’t exaggerating. “Then we better hurry up and get to your house!”

“Yay!” She ran ahead of him, only pausing a few seconds each time to let Luka catch up.

* * *

“It’s here! It’s here, it’s here it’s here!” Marinette squealed, grabbing the bubble mailer off her bed once they arrived to her house. Luka snickered as he tugged off his shoes and made himself comfortable. Marinette had made herself very comfortable in her age regression since he told her about the option, and now just the idea of a plain pink pacifier had her jumping up and down with as much excitement as he’d expect if he told her she was designing Jagged Stone’s tour outfits.

“Well?” Luka asked, “how’s it look?” Marinette jumped off the loft with her pacifier between her teeth, a huge grin spilling out the sides of the shield. “Aren’t you cute!”

She giggled and twisted at the hips, hiding her face shyly with her hair.

“Do you like it?” Luka asked. Marinette nodded, taking a seat beside Luka and removing her pacifier.

“It’s really nice…”

“…Everything okay?” He placed a hand on the small of her back, and Marinette gave a small nod, fiddling with the cloudy teat.

“Everything’s okay…I’m happy, really.”

“Buuuut?”

“…Are you okay with it, really? This is all just for me, just to make me feel better…are you sure this is okay?”

“Marinette,” Luka started, shifting to face the girl and take her hands in his, “you’re so important to me, and I’m happy when you’re happy. I _like_ taking care of you, and I like helping you with this. I wouldn’t have brought it up to you if I didn’t like helping. This whole thing is _more_ than okay. Okay?”

She nodded, sniffling a bit and wiping her nose with the back of her hand. “Thanks, Luka…”

“Of course, baby girl…now, pop that paci back in, we have some cartoons to watch!”

“Yayyyyyyy!”

The two made themselves comfortable on the chaise, watching as much Sofia the First as Marinette could possibly want until she fell asleep. The scene was so soft, and the both felt so at ease and happy together, glad to have this dynamic just for themselves.

**Notes for the Chapter:**

> hey sorry it took so long to update again but!! i'm back!!


End file.
